The detection of microorganisms in environmental water or drinking water is very important to environmental sanitation and public health. There is a need in detecting pathogens in environmental water or drinking water effectively and rapidly such as the detection of Escherichia coli, Staphylococcus aureus, Salmonella spp., Vibrio cholerae, Helicobacter pylori, Shigella sonnei, Legionella spp., Pseudomonas aeruginosa and Enterovirus.
Organisms of the genus Shigella cause classic bacillary dysentery that is characterized by severe diarrhea, fever and abdominal pain. Shigella is one of Enterobacteriacea and can be classified into four species: S. dysenteriae, S. flexneri, S. boydii and S. sonnei. Shigella spp. is typically associated with self-limiting infections that are rarely fatal except in children or the elderly. Infection with S. dysenteriae can cause a severe form of the disease with up to 20% of cases proving fatal, such as hemorrhagic colitis and hemolytic uremic syndrome. Although the syndromes caused by the infection with S. flexneri, S. boydii and S. sonnei are not so severe and can be cured by antibiotics, the general use of antibiotics results in the production of strains resistant against antibiotics. Moreover, S. sonnei infection frequently occurs in the industrially developed area. The S. sonnei infection will be popular in the industrial area of a high population density. Normally, the human by intake of 10–100 bacteria cells will be infected (DuPont et al., 1989, J. infect. Dis.).
Traditionally, two methods are used in the detection of microorganisms in solution samples. One is directed to a method comprising the steps of filtering a water sample by a filter, culturing the filter in a petri dish and then observing the appearance of the colonies and calculating the numbers of the colonies. The other one is directed to a biochemical analysis method comprising the steps of culturing the samples with a medium broth, using specific agents to carry out a biochemical reaction with the microbial cultures and then analyzing the results of the biochemical reaction. Recently, polymerase chain reaction (PCR) methods and hybridization methods are developed to detect the microorganisms in water samples, which require extracting the nucleic acids of the microorganism from the samples. Bej et al. disclose a method of filtering a solution sample with a filter, adding the filter to sterile water and then shaking and treating the filter with a mixed liquid containing ethanol and dry ice (ethanol-dry ice bath) and warm water (45 to 50° C.) alternatively for five times (Applied and Environmental Microbiology, April 1991, 57(4): 1013–1017). However, since the method needs an alternative treatment with high temperature and low temperature, it is complicated and time-consuming.
Morris et al. indicated that the isolation percent of Shigella spp. samples was lower than 25%. That is, more than 75% of samples existing Shigella spp. could not be correctly detected (Morris et al., 1970, Appl. Microbiol.). Polymerase chain reaction (PCR) can be rapid and reliable for detecting bacteria and virus in various samples. It was described in Josephson et al., 1993, App. Environ. Microbiol that the PCR can detect the S. sonnei that cannot be cultivated. However, the method cannot specifically detect the existence of S. sonnei. Accordingly, there is a need to provide a method for a rapid and specific detection of S. sonnie in food and clinical samples and an improvement method for extracting the nucleic acids of microorganisms in a solution sample.